<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<script type="text/javascript">
			window.onload = function(){
				var id1 = document.getElementById("id1");
				var btn = document.getElementById("btn01");
				btn.onclick = function(){
					id1.style.fontSize = "20px";
				};
			};
		</script>
	</head>
	<body>
		<h1 id="id1">我的标题 1</h1>
		<button type="button" id="btn01">点我!</button>
		
		
	</body>
</html>
